Elysia
You decide to look at the book. It has a plain white cover that has a single word on it. "Merrow". Upon being opened it is revealed that this isn't quite an ordinary book. The writing on the pages is unintelligible, yet looking at it seems to send a psionic message straight to your mind...
Curious images flow through your mind, and they begin to tell a story. It states that the "Selkie" is not exclusively a term that referred to one of the great vampire clans, but also a kind of folkloric creature. This creature had the upper body of a "Poyapturan", and the images you see confirm that a Poyapturan is the kind of creature that you have been interacting with. Their lower body resembles that of a seal. This creature had the ability to "shed" their seal skin to take on the guise of a normal person, and can put the skin back on to return to the waters...
The book then tells you a story. It excludes a lot of the specific details, but the gist of it seems to be that there was once a man who stole the skin of a Selkie. He then locked it away in a box, and forced the Selkie to marry him. One day while out fishing, he realized that he forgot to take the key to the box with him, and when he returned he realized that the Selkie had opened the box and swam away. In a rage, the man tracked her down and killed her Selkie husband and children...
The last page of the book... Its a blank and totally red page.